1. Field of Invention
The present invention relates to a switching regulator, and a control circuit and method for controlling a switching regulator. Particularly, it relates to such switching regulator, control circuit, and control method which control a rectified power (an input power after rectification) within a predetermined range.
2. Description of Related Art
The output power or output current of a switching regulator is preferably controlled within a predetermined range in some applications of the switching regulator. To control the output power or output current within a predetermined range, in prior art, it is required to detect the output voltage and the output current and feedback such information to control the switching regulator.
One of the drawbacks of the aforementioned prior art is that, the detected signals related to the output voltage and the output current can not be directly electrically connected to a control circuit in an isolated switching regulator, such as an isolated AC/DC conversion circuit. The detected signals may be delivered to the control circuit by an indirect way, such as by an opto-coupling circuit, but this increases the cost, and the indirect opto-coupling is more likely to generate errors as compared to direct electrical connection.
In view of the foregoing, the present invention provides a switching regulator, and a control circuit and method for controlling a switching regulator, which detects an input voltage and an input current, and controls the rectified power within a predetermined range by a direct way, such that the output power or output current of the switching regulator may be substantially constant.